CN117794733A

CN117794733A - Multilayer structure comprising a longitudinally oriented multilayer film

Info

Publication number: CN117794733A
Application number: CN202280054178.7A
Authority: CN
Inventors: P·P·博世; L·G·Z·巴斯蒂罗
Original assignee: Dow Global Technologies LLC
Current assignee: Dow Global Technologies LLC
Priority date: 2021-08-23
Filing date: 2022-08-22
Publication date: 2024-03-29
Also published as: WO2023027987A1

Abstract

In one embodiment, a multilayer structure may include a Machine Direction Oriented (MDO) multilayer film, a first layer, and a sealant layer. The MDO multilayer film may include (i) a metal layer and (ii) an inner layer. The inner layer may comprise EVOH; PVOH; or a blend of polyethylene with an interpolymer of ethylene and methyl acrylate, ethyl acrylate, or a carboxylic acid. The first layer may be extruded onto the metal layer. The first layer may comprise an interpolymer of ethylene and acrylic acid or methacrylic acid. The interpolymer may have a melt index (I) from 5g/10 min to 20g/10 min ₂ ) An acid content of 1 to 10 wt.% and a melting temperature of 90 to 100 ℃. The sealant layer may comprise a polyethylene having a melt index (I) of 3g/10 min to 30g/10 min ₂ ) And a heat seal initiation temperature of 95 ℃ or less.

Description

Multilayer structure comprising a longitudinally oriented multilayer film

Cross Reference to Related Applications

The present application claims the benefit of U.S. provisional application Ser. No. 63/235,883, filed 8/23 at 2021, the entire disclosure of which is incorporated herein by reference.

Technical Field

The present disclosure relates to multilayer structures, and more particularly to multilayer structures including longitudinally oriented films.

Background

Although there is interest in the market place in longitudinally oriented (MDO) polyethylene films, one limitation in using MDO polyethylene films is a significant loss of sealing performance relative to other films after orientation. The sealing temperature of MDO polyethylene films is typically increased by 20 ℃ to 25 ℃ relative to other films. MDO polyethylene films are also understood to have reduced temperature resistance relative to laminated films. This combination of factors results in a very narrow sealing window and, where a heat sealing step is required, can make manufacture of articles by such MDO films challenging.

Thus, new structures that can expand the range between sealing and shrinkage in a multi-layer structure in a cost-effective manner are desired.

Disclosure of Invention

The sealant layer should generally be capable of sealing at a temperature below the degradation temperature of the other parts of the multilayer structure being sealed. For example, in some production lines, where two films are sealed together by sealing strips, the sealant layers of the two films are in contact with each other, and the sealing strips contact and heat the outer layers of the films. Heat is transferred through the outer layer of the film to the inner sealant layer which is sealed to each other. Reduced sealing temperatures are desirable because they enable reduced degradation (e.g., combustion) of other layers of the multilayer structure. In addition, the reduced sealing temperature allows for a more consistent seal because the sealing process can be performed in a wider window between the degradation temperature of the film and the seal initiation temperature of the sealant layer. Embodiments of the present disclosure address this need by providing an MDO multilayer film having a metal layer, a first layer extruded onto the metal layer, and a sealant layer in adhering contact with the first layer, as further described herein.

According to one embodiment of the present disclosure, a multilayer structure may include a Machine Direction Oriented (MDO) multilayer film, a first layer, and a sealant layer. The MDO multilayer film may include (i) a metal layer and (ii) an inner layer in adhering contact with the metal layer. The inner layer may comprise ethylene vinyl alcohol; polyvinyl alcohol; or a blend of polyethylene with an interpolymer of ethylene and methyl acrylate, ethyl acrylate, or a carboxylic acid. The first layer may be extruded onto the metal layer of the MDO multilayer film. The first layer may comprise an interpolymer of ethylene and acrylic acid or methacrylic acid. The interpolymer may have a melt index (I) from 5g/10 min to 20g/10 min ₂ ) An acid content of 1 to 10 wt.% and a melting temperature of 90 to 100 ℃. The sealant layer may be in adhering contact with the first layer. The sealant layer may comprise a polyethylene having a melt index (I) of 3g/10 min to 30g/10 min ₂ ) And a heat seal initiation temperature of 95 ℃ or less.

Although the concepts of the present disclosure are described herein primarily with reference to a machine direction oriented film having a metal layer, it is contemplated that these concepts will apply to any multilayer film.

Detailed Description

Reference will now be made in greater detail to various embodiments, examples of which are the claimed subject matter. It should be understood that the features of the multilayered structure described in the detailed description should not be construed to limit the claimed embodiments unless explicitly so described.

According to some embodiments of the disclosure, multiple layersThe structure may include a Machine Direction Oriented (MDO) multilayer film, a first layer, and a sealant layer. The Machine Direction Oriented (MDO) multilayer film may include (i) a metal layer and (ii) an inner layer in adhering contact with the metal layer. In some embodiments, the metal layer is a metallization layer. The inner layer may comprise ethylene vinyl alcohol; polyvinyl alcohol; or a blend of polyethylene with an interpolymer of ethylene and methyl acrylate, ethyl acrylate, or a carboxylic acid. The first layer may be extruded onto the metal layer of the machine direction oriented multilayer film. The first layer may comprise an interpolymer of ethylene and acrylic acid or methacrylic acid. The interpolymer may have a melt index (I) from 5g/10 min to 20g/10 min ₂ ) An acid content of 1 to 10 wt.% and a melting temperature of 90 to 100 ℃. The sealant layer may be in adhering contact with the first layer. The sealant layer may comprise a polyethylene having a melt index (I) of 3g/10 min to 30g/10 min ₂ ) And a heat seal initiation temperature of 95 ℃ or less.

According to one or more embodiments, the multilayer structure may include a machine direction oriented film. As used herein, a "machine direction oriented" film is a film formed by uniaxially stretching the film in the machine direction to improve physical and barrier properties. For example, the film may be heated and uniaxially stretched in the machine direction on a series of rolls. As used herein, the term "machine direction" means the length of a film in its direction of production. The machine direction oriented film may exhibit improved tensile properties compared to a film that has not undergone a machine direction orientation procedure.

As used herein, a "film" generally includes any continuous layer comprising a polyolefin material, which layer generally has a large aspect ratio and width to thickness ratio. In one or more embodiments, the film may comprise one or more olefin-based polymers. As used herein, the terms "olefin-based polymer," "olefin-based polymer," and "polyolefin" refer to a polymer that comprises a majority amount of an olefin monomer in polymerized form, such as ethylene or propylene (based on the weight of the polymer), and optionally may comprise one or more comonomers. The term "polymer" refers to a polymeric compound prepared by polymerizing monomers (whether of the same or different types). Thus, the generic term polymer encompasses the term "homopolymer" which is generally used to refer to polymers prepared from only one type of monomer, as well as "copolymer" which refers to polymers prepared from two or more different monomers. The films described herein may be multilayer films comprising more than one layer.

As used herein, "interpolymer" may refer to a polymer derived from more than one monomer species. For example, the interpolymer may comprise 2, 3, 4, or more than 4 monomer species. As used herein, "terpolymer" may refer to a polymer derived from three monomer species. The terpolymer may be characterized as a random interpolymer, a periodic interpolymer, a statistical interpolymer, or a block interpolymer. As used herein, "random interpolymer" may refer to an interpolymer comprising units of a plurality of monomer species distributed in a random sequence. As used herein, a "periodic interpolymer" may refer to an interpolymer that comprises units of three or more monomeric species arranged in a repeating pattern. As used herein, "statistical interpolymer" may refer to an interpolymer that comprises two or more monomer units and whose distribution complies with statistical rules. As used herein, a "block interpolymer" may refer to an interpolymer that comprises two or more monomer units, and wherein the monomer units are clustered with similar monomer units. For example, the block interpolymer may have a structure in the form of aaaabbbcc.

As used herein, "polyethylene" or "ethylene-based polymer" shall mean a polymer comprising greater than 50 mole% of units derived from ethylene monomers. This includes ethylene-based homopolymers, ethylene copolymers (meaning units derived from ethylene and additional monomers) and ethylene interpolymers (meaning units derived from ethylene and at least one additional comonomer). These comonomers may include C ₃ -C ₁₂ Alpha-olefin comonomers, or may include polar comonomers. These polar comonomers may include, but are not limited to, those having carboxylic acid, acrylate, or acetate functionality, such as methacrylic acid, acrylic acid, vinyl acetate, methyl acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, glycidyl methacrylate, and monoethyl maleate. Forms of polyethylene include, but are not limited to, low Density Polyethylene (LDPE); linear low density polyethylene (L)LDPE); ultra Low Density Polyethylene (ULDPE); very Low Density Polyethylene (VLDPE); single site catalysed linear low density polyethylene comprising linear and substantially linear low density resins (m-LLDPE); medium Density Polyethylene (MDPE); and High Density Polyethylene (HDPE).

In addition, as described herein, the term "LDPE" may also be referred to as "high pressure ethylene polymer" or "highly branched polyethylene" and is defined to mean that the polymer may be partially or fully homo-or co-polymerized in an autoclave or tubular reactor at a pressure above 14,500psi (100 MPa) with the use of a free radical initiator such as peroxide (see, e.g., U.S.4,599,392, which is hereby incorporated by reference). LDPE resins typically have a density in the range of 0.916g/cm to 0.940 g/cm.

As described herein, the term "LLDPE" can include resins made using Ziegler-Natta (Ziegler-Natta) catalyst systems, as well as resins made using single site catalysts, including but not limited to dual metallocene catalysts (sometimes referred to as "m-LLDPE"), phosphinimines, and constrained geometry catalysts; and resins made using post-metallocene, molecular catalysts including, but not limited to, bis (biphenylphenoxy) catalysts (also known as polyvalent aryloxyether catalysts). LLDPE includes linear, substantially linear or heterogeneous ethylene-based copolymers or homopolymers. LLDPE contains less long chain branching than LDPE and comprises: substantially linear ethylene polymers, further defined in U.S. Pat. No. 5,272,236, U.S. Pat. No. 5,278,272, U.S. Pat. No. 5,582,923, and U.S. Pat. No. 5,733,155; homogeneously branched ethylene polymers, such as the homogeneously branched ethylene polymers in U.S. Pat. No. 3,645,992; heterogeneously branched ethylene polymers, such as heterogeneously branched ethylene polymers prepared according to the method disclosed in U.S. Pat. No. 4,076,698; and blends thereof (such as those disclosed in U.S. Pat. No. 3,914,342 or U.S. Pat. No. 5,854,045). The LLDPE resin can be prepared via gas phase, solution phase or slurry polymerization or any combination thereof using any type of reactor or reactor configuration known in the art. The LLDPE resin can be prepared via gas phase, solution phase or slurry polymerization or any combination thereof using any type of reactor or reactor configuration known in the art.

The term "ULDPE" is defined as a polyethylene-based copolymer having a density in the range of 0.895g/cc to 0.915 g/cc.

The term "MDPE" refers to polyethylene having a density of 0.926g/cc to 0.935 g/cc. "MDPE" is typically prepared using chromium or Ziegler-Natta catalysts or using single site catalysts (including but not limited to dual metallocene catalysts and constrained geometry catalysts).

In addition, as described herein, the term "HDPE" refers to polyethylenes having a density of about 0.940g/cm or greater, which are typically prepared with ziegler-natta catalysts, chromium catalysts or even metallocene catalysts.

The multilayer structure may include an MDO multilayer film, a first layer, and a sealant layer. As used herein, "multi-layer structure" means any structure having more than one layer. For example, a multilayer structure (e.g., film) may have two, three, four, five or more layers. The multi-layer structure may be described as having layers denoted by letters. For example, a three-layer structure having a core layer B and two outer layers a and C may be designated a/B/C. Also, a structure having two core layers B and C and two outer layers a and D will be denoted as a/B/C/D.

The MDO multilayer film may have a thickness of 10 μm to 100 μm. For example, the MDO multilayer film may have a thickness of 10 μm to 90 μm, 10 μm to 75 μm, 10 μm to 60 μm, 10 μm to 45 μm, 10 μm to 30 μm, 20 μm to 100 μm, 20 μm to 90 μm, 20 μm to 75 μm, 20 μm to 60 μm, 20 μm to 45 μm, 20 μm to 30 μm, or any subset thereof.

According to one or more embodiments, the machine direction oriented film may have a melting point of less than or equal to 150 ℃, such as less than or equal to 145 ℃, or even less than or equal to 140 ℃. This is in contrast to other films which may have a larger melting point. For example, the polypropylene film may have a melting point greater than 150 ℃ and the polyethylene terephthalate film may have a melting point greater than 250 ℃.

The MDO multilayer film may include (i) a metal layer and (ii) an inner layer in adhering contact with the metal layer. The term "adhesion contact" and similar terms mean that one surface of one layer and one surface of the other layer touch and come into adhesive contact with each other such that one layer cannot be removed from the other layer without damaging the interlayer surfaces (i.e., the contact surfaces) of the two layers.

The metal layer may be a metallized layer applied to the outer layer of the MDO multilayer film using vacuum metallization. Vacuum metallization is a well known technique for depositing metals, in which a metal source is evaporated in a vacuum environment, and metal vapor condenses on the surface of the film as it passes through a vacuum chamber, forming a thin layer.

Metals that may be deposited to form the metallization layer include Al, zn, au, ag, cu, ni, cr, ge, se, ti, sn or their oxides. In some embodiments, the metallization layer is made of aluminum or aluminum oxide (A1 ₂ 0 ₃ ) And (5) forming. The metallization layer may also comprise metalloid silicon or an oxide thereof. According to some embodiments, the metallization layer may comprise aluminum, silicon, or oxides thereof.

The metallization layer may advantageously provide a good barrier to oxygen and water vapor. The combination of the MDO multilayer film with a metallized layer deposited on a specific outer surface may provide a synergistic combination of both mechanical and barrier properties.

In some embodiments, the metallized layer may be a decorative layer that is included to increase the gloss of the flexible package. Those skilled in the art are familiar with a variety of applicable metallization techniques. These metallization techniques may include, but are not limited to, physical vapor deposition or vacuum metallization. Although various thicknesses are contemplated, in one or more embodiments, the metallization layer may have a thickness of less than 100 nanometers, or 10 nanometers to 80 nanometers, or 20 nanometers to 60 nanometers.

In some embodiments, the metal layer may be a foil layer adhered to the remainder of the MDO multilayer film with a tie layer. In embodiments in which the metal layer is a foil layer, the foil layer may have a thickness of 6 μm to 15 μm, 6 μm to 12 μm, 10 μm to 15 μm, 8 μm to 12 μm, or any subset thereof.

In embodiments in which a tie layer is present, the tie layer may comprise maleated polyethylene, a copolymer of ethylene and a carboxylic acid, or a combination thereof. As used herein, a "maleated" material is a material that comprises a salt or ester of maleic acid.

Referring again to the MDO multilayer film, the MDO multilayer film may have five layers and a structure A/B/C/D/E, where layer A is the inner layer and the metallized layer is on the surface of layer A. Layer a may have a thickness of 10% to 20% of the total thickness of the MDO multilayer film. Layer B may have a thickness of 10% to 20% of the total thickness of the MDO multilayer film. Layer C may have a thickness of 20% to 40% of the total thickness of the MDO multilayer film. Layer D may have a thickness of 10% to 30% of the total thickness of the MDO multilayer film. Layer E may have a thickness of 10% to 30% of the total thickness of the MDO multilayer film. These layers may be extruded one on top of the other. The MDO multilayer film may have one or more polyethylene layers. For example, the MDO multilayer film may have 2, 3, 4, or 5 polyethylene layers.

As previously mentioned, layer a as the inner layer comprises at least one polymer having at least one polar monomer. For example, the inner layer (layer a) may comprise one or more of the following: ethylene vinyl alcohol (EVOH), polyvinyl alcohol (PVOH), polyethylene resins, mixtures of polyethylene resins with interpolymers of ethylene and acrylic acid esters, or mixtures of polyethylene resins with interpolymers of ethylene and carboxylic acid.

For an inner layer embodiment comprising EVOH, the EVOH may have a weight of 0.90g/cm ³ To 1.40g/cm ³ Or 0.95g/cm ³ To 1.20g/cm ³ Or the density of any subset thereof. Layer a may have a melt index of 0.70 g/10 min to 1.9 g/10 min. The EVOH may have a melt index of 1.00 g/10 min to 3.00 g/10 min, or 1.00 g/10 min to 2.50 g/10 min, or 1.50 g/10 min to 2.00 g/10 min, or any subset thereof. The EVOH may have a melt temperature of 120 ℃ to 250 ℃, or 150 ℃ to 200 ℃, or any subset thereof. Suitable commercial examples of EVOH may include commercial grades Eval E171B, F B and J171B available from EVAL Europe NV corporation (EVAL Europe NV).

For an inner part comprising polyethylene resinLayer embodiment, the polyethylene may be a polyethylene having a weight of 0.940g/cm ³ To 0.975g/cm ³ Or 0.945g/cm ³ To 0.970g/cm ³ Or 0.950g/cm ³ To 0.965g/cm ³ Or any subset thereof. The ethylene-alpha-olefin copolymer may have a melt index of 0.5 g/10 min to 3.00 g/10 min, or 0.75 g/10 min to 2.00 g/10 min, or any subset thereof. The ethylene-alpha-olefin copolymer may be LLDPE. Suitable commercial LLDPE resins may include DOWLEX from Dow Inc. (Dow Inc., midland, mich.) of Midland, mich ^TM 2750ST. Additionally, suitable commercial examples may include ELITE from Dow chemical company of Midland, michigan ^TM 5960G1 reinforced polyethylene.

For inner layer embodiments comprising interpolymers of ethylene and an acrylate, the acrylate may include any suitable C ₂ -C ₁₂ Acrylates such as methyl acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate and glycidyl methacrylate. In one embodiment, the acrylate comprises n-butyl acrylate. The ethylene-acrylate comonomer may comprise 10 to 40 wt% acrylate, or 15 to 35 wt% or 20 to 30 wt% acrylate, with the remainder comprising ethylene monomer, in terms of monomer amount. The interpolymer of ethylene and acrylate may have a weight of 0.910g/cm ³ To 0.955g/cm ³ Or 0.920g/cm ³ To 0.950g/cm ³ Or 0.925g/cm ³ To 0.945g/cm ³ Or the density of any subset thereof. The interpolymer of ethylene and acrylate may have a melt index from 0.5 g/10 min to 5.00 g/10 min, or from 1.00 g/10 min to 4.50 g/10 min, or from 1.50 g/10 min to 4.00 g/10 min, or any subset thereof. Suitable commercial examples may include ELVALOY from the dow chemical company of midland, michigan ^TM AC stages 1224, 3117 and 3427.

Layer B may also comprise one or more polyethylenes. The polyethylene may have a weight of 0.910g/cm ³ To 0.950g/cm ³ Or 0.915g/cm ³ To 0.945g/cm ³ Is a density of (3). In some embodiments, low density polyethylene (0.910 g/cm ³ To 0.920g/cm ³ ) And high density polyethylene (0.930 g/cm) ³ To 0.945g/cm ³ ) Is a mixture of (a) and (b). The polyethylene may have a melt index of 0.25 g/10 min to 2.0 g/10 min, or 0.50 g/10 min to 1.5 g/10 min, or 0.75 g/10 min to 1.25 g/10 min, or any subset thereof. The polyethylene in layer B may have a melting temperature of 100 ℃ to 140 ℃, or 110 ℃ to 130 ℃, or 115 ℃ to 130 ℃, or any subset thereof. Suitable commercial examples may include ELITE from Dow chemical company of Midland, michigan ^TM 5400GS and 5940ST reinforced polyethylenes, which can be used alone or in blends.

In other embodiments, layer B may comprise a tie layer comprising an ethylene and acid copolymer. In one or more embodiments, the tie layer may include an anhydride grafted ethylene/a-olefin interpolymer. As used herein, the term "anhydride grafted ethylene/a-olefin interpolymer" refers to an ethylene/a-olefin interpolymer that comprises at least one anhydride group attached by a covalent bond. The anhydride grafted ethylene/alpha-olefin interpolymer may be an ethylene-based polymer to which the anhydride grafted monomer is grafted. Suitable ethylene-based polymers for low melt viscosity maleic anhydride grafted polyolefins include, but are not limited to, polyethylene homopolymers and copolymers with alpha-olefins, copolymers of ethylene with vinyl acetate, and copolymers of ethylene with one or more alkyl (meth) acrylates. In particular embodiments, the anhydride grafted ethylene/α -olefin interpolymer may comprise maleic anhydride grafted Linear Low Density Polyethylene (LLDPE).

In one or more embodiments, the anhydride grafted ethylene/α -olefin interpolymer comprises from up to 10 weight percent, up to 5 weight percent, or from 0.1 weight percent to 4 weight percent maleic anhydride grafted monomer, based on the total weight of the anhydride grafted ethylene/α -olefin interpolymer.

Examples of anhydride grafted moieties may include, but are not limited to, maleic anhydride, citraconic anhydride, 2-methyl maleic anhydride, 2-chloromaleic anhydride, 2, 3-dimethyl maleic anhydride, bicyclo [2, 1] -5-heptene-2, 3-dicarboxylic anhydride and 4-methyl-4-cyclohexene-1, 2-dicarboxylic anhydride, bicyclo (2.2.2) oct-5-ene-2, 3-dicarboxylic anhydride, ortho-octahydronaphthalene-2, 3-dicarboxylic anhydride, 2-oxa-1, 3-diketopiro (4.4) non-7-ene, bicyclo (2.2.1) hept-5-ene-2, 3-dicarboxylic anhydride, tetrahydrophthalic anhydride, norbornen-5-ene-2, 3-dicarboxylic anhydride, nadic anhydride, methylnadic anhydride, norbornene dicarboxylic anhydride, methylnorbornenedicarboxylic anhydride, and x-methyl-bicyclo (2.2.1) hept-5-ene-2, 3-dicarboxylic anhydride. In one embodiment, the anhydride grafted moiety comprises maleic anhydride.

In a further embodiment, the anhydride grafted ethylene/α -olefin interpolymer has a weight ratio of 0.890g/cm ³ To 0.940g/cm ³ As measured according to ASTM method No. D792-91. Other density ranges may be 0.900g/cm ³ To 0.930g/cm ³ Or 0.905g/cm ³ To 0.915g/cm ³ . In one or more embodiments, the anhydride grafted ethylene/α -olefin interpolymer may have a melt index (I) from 0.5 g/10 min to 3 g/10 min, or from 1 g/10 min to 2 g/10 min, or from 1.5 g/10 min to 2.0 g/10 min, as measured according to ASTM method D1238 at 190 ℃ and 2.16kg ₂ ). Suitable commercial examples of anhydride grafted ethylene/alpha-olefin interpolymers may include BYNEL from Dow chemical company of Midlan, michigan ^TM 41E687B。

Layers C and D may also comprise one or more polyethylenes. Similar to layer B, the polyethylene may have a weight of 0.910g/cm ³ To 0.950g/cm ³ Or 0.915g/cm ³ To 0.945g/cm ³ Is a density of (3). In some embodiments, low density polyethylene (0.910 g/cm ³ To 0.920g/cm ³ ) And high density polyethylene (0.930 g/cm) ³ To 0.945g/cm ³ ) Is a mixture of (a) and (b). The polyethylene may have a melt index of 0.25 g/10 min to 2.0 g/10 min, or 0.50 g/10 min to 1.5 g/10 min, or 0.75 g/10 min to 1.25 g/10 min, or any subset thereof. The polyethylene in layer B may have a melting temperature of 100 ℃ to 140 ℃, or 110 ℃ to 130 ℃, or 115 ℃ to 130 ℃, or any subset thereof. Suitable commercial examples may include those from Mide, michigan ELITE from Dow chemical Co., lanshi ^TM 5400GS and 5940ST reinforced polyethylenes, which can be used alone or in blends.

Layer E may also comprise one or more polyethylene resins. The polyethylene may be of 0.940g/cm ³ To 0.975g/cm ³ Or 0.945g/cm ³ To 0.970g/cm ³ Or 0.950g/cm ³ To 0.965g/cm ³ Or any subset thereof. The ethylene-alpha-olefin copolymer may have a melt index of 0.5 g/10 min to 3.00 g/10 min, 0.75 g/10 min to 2.00 g/10 min, or any subset thereof. The ethylene-alpha-olefin copolymer may be LLDPE. Suitable commercial LLDPE resins may include DOWLEX from Dow chemical company of Midland, michigan ^TM 2750ST. Additionally, suitable commercial examples may include ELITE from Dow chemical company of Midland, michigan ^TM 5960G1 reinforced polyethylene.

Referring again to the first layer as described above, the first layer may be extrusion coated onto the metallized layer of the machine direction oriented multilayer film. As described herein, extruding the first layer may include forming the first layer through a die to form a desired layer thickness and other physical properties. The polymer blends of the present disclosure may be prepared by melt blending the specified amounts of the components with a twin screw extruder and then feeding into a extrusion coater (or other apparatus) used in film manufacture. Such polymer blends may also be prepared by tumble blending the specified amounts of the components and then feeding into a press (or other apparatus) for film manufacture. In some embodiments, the polymer blend may be in pellet form. For example, based on the teachings herein, the individual components may be melt blended and then formed into pellets using a twin screw extruder or other techniques known to those skilled in the art. In some embodiments, the polymer blend may include a combination of compounded pellets and additional polymer that is tumble blended prior to feeding into the extrusion coater.

The first layer may be extruded onto the MDO multilayer film at a load of 2 grams per square meter (gsm) to 16 gsm. For example, the first layer may have a loading of 2gsm to 12gsm, 2gsm to 8gsm, 2gsm to 6gsm, 4gsm to 16gsm, 4gsm to 12gsm, 4gsm to 8gsm, or any subset thereof.

The interpolymer of the first layer can comprise from 50% to 98% by weight ethylene monomer. For example, the interpolymer of the first layer may include ethylene from 60 wt% to 98 wt%, from 70 wt% to 98 wt%, from 80 wt% to 98 wt%, from 90 wt% to 98 wt%, from 50 wt% to 90 wt%, from 50 wt% to 80 wt%, from 50 wt% to 70 wt%, from 50 wt% to 60 wt%, from 60 wt% to 90 wt%, from 70 wt% to 80 wt%, or any subset thereof.

The first layer may comprise an interpolymer of ethylene and acrylic acid or methacrylic acid.

The interpolymer of the first layer can have a melt index (I) ₂ ). For example, the interpolymer of the first layer can have an I of from 5g/10 min to 18g/10 min, from 8g/10 min to 20g/10 min, from 8g/10 min to 18g/10 min, from 5g/10 min to 15g/10 min, from 12g/10 min to 20g/10 min, from 12g/10 min to 15g/10 min, or any subset thereof ₂ . As used herein, "melt index" (I ₂ ) Is a measure of the melt flow rate of the polymer as measured by ASTM D1238 at a temperature of 190 ℃ and a load of 2.16 kg. "melt index" may also be referred to herein as "I ₂ "and" melt flow rate ".

The interpolymer of the first layer can have an acid content of from 1 to 10 weight percent (wt%). As used herein, "acid content" refers to the amount of acrylic acid relative to the total weight of the interpolymer. For example, the interpolymer of the first layer can have an acid content of from 1 wt.% to 9 wt.%, from 1 wt.% to 8 wt.%, from 1 wt.% to 6 wt.%, from 2 wt.% to 10 wt.%, from 3 wt.% to 10 wt.%, from 4 wt.% to 10 wt.%, from 2 wt.% to 8 wt.%, from 3 wt.% to 7 wt.%, from 4 wt.% to 6 wt.%, or any subset thereof.

The interpolymer of the first layer can have a melting temperature of from 90 ℃ to 100 ℃. For example, the interpolymer of the first layer can have a melting temperature of from 90 ℃ to 98 ℃, from 90 ℃ to 96 ℃, from 90 ℃ to 94 ℃, from 90 ℃ to 92 ℃, from 92 ℃ to 98 ℃, from 92 ℃ to 96 ℃, from 92 ℃ to 94 ℃, from 94 ℃ to 98 ℃, from 94 ℃ to 96 ℃, from 96 ℃ to 98 ℃, or any subset thereof.

The interpolymer of the first layer may be a terpolymer of: ethylene; acrylic acid or methacrylic acid; and alkyl acrylates. For example, the interpolymer of the first layer may be a terpolymer of ethylene, acrylic acid and alkyl acrylate, or the interpolymer of the first layer may be a terpolymer of ethylene, methacrylic acid and alkyl acrylate. In one or more embodiments of the present disclosure, the interpolymer may be NUCREL available from Dow chemical company of Midland, mich ^TM Members of the family.

The multilayer structure may include a sealant layer. The sealant layer may be generally heated and pressurized to seal the two multilayer structures to each other through its sealant layer. The sealant layer may be in adhering contact with the first layer.

In one or more embodiments, the sealant layer can be in adhering contact with the first layer. In one or more embodiments, the sealant layer can be extruded onto the first layer. Extruding the sealant layer may include forming the sealant layer through a die to form a desired layer thickness and other physical properties, as described herein.

The sealant layer may be extruded onto the first layer film at a load of 10 grams gsm to 30 gsm. For example, the sealant layer may have a loading of 10gsm to 26gsm, 10gsm to 24gsm, 10gsm to 21gsm, 14gsm to 30gsm, 14gsm to 26gsm, 14gsm to 24gsm, 14gsm to 21gsm, 18gsm to 30gsm, 18gsm to 24gsm, 18gsm to 21gsm, 18gsm to 20gsm, or any subset thereof.

The sealant layer may comprise 60 to 85 wt% of at least one polyethylene. For example, the sealant layer may include 60 to 80 wt%, 60 to 75 wt%, 60 to 70 wt%, 65 to 85 wt%, 70 to 85 wt%, 75 to 85 wt%, 65 to 80 wt%, 70 to 75 wt%, or any subset thereof of at least one polyethylene.

The sealant layer may comprise polyethylene having a density of 0.870 grams per cubic centimeter (g/cc) to 0.911 g/cc. For example, the sealant layer may comprise polyethylene having a density of 0.870g/cc to 0.901g/cc, 0.870g/cc to 0.891g/cc, 0.870g/cc to 0.881g/cc, 0.880g/cc to 0.911g/cc, 0.890g/cc to 0.911g/cc, 0.901g/cc to 0.911g/cc, 0.880g/cc to 0.901g/cc, or any subset thereof.

The sealant layer may comprise a polymer having a melt index (I) of at least 3g/10 min ₂ ) Is a polyethylene of (a). For example, the sealant layer may comprise polyethylene having an I of at least 4g/10 min, at least 5g/10 min, at least 7.5g/10 min, at least 10g/10 min, at least 15g/10 min, at least 20g/10 min, at least 25g/10 min, or even at least 30g/10 min ₂ 。

The sealant layer may comprise a polymer having a melt index (I) of 3g/10 min to 30g/10 min ₂ ) Is a polyethylene of (a). For example, the sealant layer may comprise a polymer having a melt index (I) of 3g/10 min to 25g/10 min, 3g/10 min to 15g/10 min, 3g/10 min to 10g/10 min, 8g/10 min to 30g/10 min, 8g/10 min to 20g/10 min, 16g/10 min to 30g/10 min, 16g/10 min to 25g/10 min, or any subset thereof ₂ ) Is a polyethylene of (a). As used herein, melt index (I ₂ ) Is a measure of the melt flow rate of the polymer as measured by ASTM D1238 at a temperature of 190 ℃ and a load of 2.16 kg.

The sealant layer may comprise polyethylene having a heat seal initiation temperature of 95 ℃ or less. For example, the sealant layer can comprise polyethylene having a heat seal initiation temperature of 92.5 ℃ or less, 90 ℃ or less, 87.5 ℃ or less, 85 ℃ or less, 82.5 ℃ or less, 80 ℃ or less, 75 ℃ or less, or even 70 ℃ or less.

In one or more embodiments, the sealant layer may comprise a low density polyethylene.

According to one or more embodiments, the sealant layer may include 15 to 40 weight percent (wt.%) of the low density polyethylene based on the total weight of the sealant layer. For example, the sealant layer may comprise 15 to 20 wt%, 20 to 25 wt%, 25 to 30 wt%, 30 to 35 wt%, 35 to 40 wt%, or a combination of any of these ranges of low density polyethylene, based on the total weight of the sealant layer. In further embodiments, the sealant layer may include 15 to 30 wt% of the low density polyethylene based on the total weight of the sealant layer.

In one or more embodiments, the low density polyethylene of the sealant layer may have a melt index (I) of 0.9g/10 min to 3.5g/10 min ₂ ). For example, the low density polyethylene of the sealant layer may have a melt index of 0.9g/10 min to 3.0g/10 min, 0.9g/10 min to 2.8g/10 min, 0.9g/10 min to 2.5g/10 min, 1.1g/10 min to 3.5g/10 min, 1.4g/10 min to 3.5g/10 min, 1.1g/10 min to 3.0g/10 min, 1.3g/10 min to 2.5g/10 min, or any subset thereof.

In one or more embodiments, the low density polyethylene of the sealant layer may be selected from the group consisting of a sealant having a density of 0.918g/cm ³ DOW having a density of 2.3g/10 min, a melt index of 110℃and a melting point of ^TM LDPE 770G (commercially available from Dow chemical company of Midland, michigan), or having a weight of 0.918G/cm ³ AGILITY with a density of 1.5g/10 min and a melt index of 1.5g/10 min ^TM EC 7220Performance LDPE (commercially available from dow chemical company, midland, michigan). However, other LDPE are contemplated for use in the sealant layer, and embodiments described herein are not limited to embodiments that include these polymers.

The sealant layer may also comprise a propylene-based plastomer. As used herein, "propylene-based plastomer" refers to a plastomer comprising greater than 50 mole percent of units derived from propylene monomers. This includes propylene-based homopolymers or interpolymers (meaning units derived from two or more monomers). Plastomers are generally understood to be polymeric materials that combine the qualities of an elastomer and a thermoplastic.

According to one or more embodiments, the sealant layer may include 60 to 85 wt% of the propylene-based plastomer based on the total weight of the sealant layer. For example, the sealant layer may comprise 60 to 65 wt%, 65 to 70 wt%, 70 to 75 wt%, 75 to 80 wt%, 80 to 85 wt%, or any combination of these ranges of propylene-based plastomers, based on the total weight of the sealant layer.

According to one or more embodiments, the propylene-based plastomer may have a 0.890g/cm ³ Or less. For example, the propylene-based plastomer may have a content of 0.860g/cm ³ To 0.890g/cm ³ Such as 0.860g/cm ³ To 0.865g/cm ³ 、0.865g/cm ³ To 0.870g/cm ³ 、0.870g/cm ³ To 0.875g/cm ³ 、0.875g/cm ³ To 0.880g/cm ³ 、0.880g/cm ³ To 0.885g/cm ³ 、0.885g/cm ³ To 0.890g/cm ³ Or a density of any combination of these ranges.

In one or more embodiments, the propylene-based plastomer may have a melt index (I) of at least 8g/10 minutes ₂ ) (at 230℃and 2.16 kg). For example, the propylene-based plastomer may have a melt flow rate (at 230 ℃ and 2.16 kg) of 8g/10 min to 35g/10 min, such as 8g/10 min to 15g/10 min, 15g/10 min to 20g/10 min, 20g/10 min to 25g/10 min, 25g/10 min to 30g/10 min, 30g/10 min to 35g/10 min, or any combination of these ranges. Unless otherwise specified, melt index (I ₂ ) Measurements were made according to ASTM D1238-10, condition 230 ℃/2.16kg, and reported in grams eluted every 10 minutes.

In one or more embodiments, the propylene-based plastomer may have a melting point of 70 ℃ to 100 ℃. For example, the propylene-based plastomer may have a melting point of 70 ℃ to 80 ℃, 80 ℃ to 90 ℃, 90 ℃ to 100 ℃, or any combination of these ranges.

In one or more embodiments, the propylene-based plastomer may be an interpolymer comprising propylene and ethylene units. According to one or more embodiments, the propylene-based plastomer may have an ethylene content of from 2 mole% to 12 mole%. For example, the propylene-based plastomer may have an ethylene content of from 2 mole% to 4 mole%, from 4 mole% to 6 mole%, from 6 mole% to 8 mole%, from 8 mole% to 10 mole%, from 10 mole% to 12 mole%, or any combination of these ranges.

In one or more embodiments, the propylene-based plastomer may be VERSIFY ^TM 4200 plastomer (commercially available from Dow chemical company of Midland, michigan) having a weight of 0.876g/cm ³ A melt index of 25g/10 min and a melting point of 84 ℃. However, other propylene-based plastomers are contemplated for use in the sealant layer, and embodiments described herein are not limited to embodiments including these polymers.

According to one or more embodiments, the sealant layer may comprise a combination of low density polyethylene and propylene-based plastomer. For example, the sealant layer may include 15 to 40 wt% low density polyethylene and 60 to 85 wt% propylene-based plastomer based on the total weight of the sealant layer.

Embodiments of the present disclosure also relate to articles, such as packages, formed from the multilayer structures of the present disclosure. Such packages may be formed from any of the multilayer structures of the present disclosure described herein. Examples of such articles may include flexible packages, pouches, stand-up pouches, and pre-made packages or pouches. According to particular embodiments of the present disclosure, the article may be a pouch.

The pouch may have a length of at least 25 mm. For example, the pouch may have a length of at least 50mm, at least 75mm, at least 100mm, at least 150mm, or at least 200 mm. The pouch may have a width of at least 25 mm. For example, the pouch may have a width of at least 50mm, at least 75mm, at least 100mm, at least 150mm, or at least 200 mm.

The pouch may have a volume of at least 25 milliliters (ml). For example, the pouch can have a volume of at least 50ml, at least 75ml, at least 100ml, at least 150ml, at least 200ml, at least 250ml, at least 300ml, at least 400ml, at least 500ml, at least 750ml, at least 1000ml, at least 1500ml, at least 2000ml, or at least 2500 ml.

The pouch may have a sealing layer. The sealing layer may be the point at which the two layers of the pouch fuse together under heat and pressure. The sealing layer may have a peel strength of at least 3 newtons per 15mm seal width (N/15 mm). For example, the sealing layer may have a peel strength of at least 4N/15mm, at least 5N/15mm, or at least 6N/15 mm. Seal strength may be measured according to ASTM D903.

Examples

Sample pouches are prepared with an MDO multilayer film, a first layer extruded onto the MDO multilayer film, and a sealant layer in adhering contact with the first layer.

The MDO multilayer film had a total thickness of 25. Mu.m. The films are arranged in the order A/B/C/D/E. Each of the respective layers comprises 15%/15%/30%/20%/20% of the thickness of the MDO multilayer film.

Table 1: composition of the multilayer film

Layer a comprises 15% of the total thickness of the MDO multilayer film and comprises EVOH Eval J171. Layer B comprises 15% of the total thickness of the MDO multilayer film and comprises Bynel 41E687. Layer C comprises 30% of the total thickness of the multilayer film and comprises 80% Elite 5940ST+20% ELITE ^TM 5400GS. Layer D comprises 20% of the total thickness of the MDO multilayer film and comprises ELITE ^TM 5940ST. Layer E comprises 20% of the total thickness of the MDO multilayer film and comprises ELITE ^TM 5960G1。

The MDO film used as a metallized substrate described above was prepared on a Hosokawa-Alpine 5 layer blown film line with screw settings of 65mm/65mm/90mm/65mm/65mm, respectively, and die diameter of 400mm. The primary film prior to MDO had a thickness of 130 μm. The draw speed (take off speed) was 16.1 meters per minute (meters per minute). The output was 370 kg/hr. The blow-up ratio (BUR) was 3.0.

The temperature profile for each extruder is as follows: a=225 ℃ in all regions; b=200 ℃ in all regions; c=200 ℃ in all regions; d=220 ℃ in all regions; e=225 ℃ in all regions; and die = 228 ℃ in all areas.

Then, the formed film was subjected to MDO stretching to form an MDO film. The stretching step was performed in a Hosokawa-Alpine MDO unit equipped with four preheaters and four annealing and cooling rolls. The speeds and ratios in the relevant parts of the system are: intake rate was 16.1 meters/minute; the discharge speed was 87.2; the overall draw ratio was 5.43. The relevant temperatures are: preheating 1=105 ℃; preheating 2=115 ℃; stretching 1=115 ℃; stretching 2=115 ℃; annealing = 110 ℃; and cooling = 75 ℃.

The MDO base film was further metallized by vacuum deposition using the K5 Expert System (K5 Expert System) from Bobst (Bobst). A metallization layer having a thickness of 30nm is deposited on the surface of layer a opposite to the surface of layer a facing layer B.

Placing the MDO base film under a pressure of 10 ^-4 In a vacuum chamber of the tray. An aluminum wire was placed in the vacuum chamber and heated to 1400 ℃. The MDO substrate film was then passed through the vacuum chamber at a rate of 500 meters per minute. The final coating thickness of the aluminum layer was about 30nm.

The first layer was then extruded onto an MDO multilayer film and contained 6 grams per square meter (gsm) NUCREL ^TM 3990. The polymer was coated using an ErWePa extrusion line using a melt temperature of 285℃and a line speed of 100 meters per minute and an air gap of 250 mm. All other conditions are typical of this well-known processing technique. The first layer is in direct contact with layer E of the MDO film.

Extruding a sealant layer onto the first layer and comprising 19gsm of blend comprising 80 wt% AFFINITY ^TM PL1280 (Dow chemical Co.) and 20 wt% AGILITY ^TM EC7220. The processing conditions and machine settings are the same as those of the layers described above. The total thickness of the first layer and the sealant layer was 25 μm.

Example 1: small bag

A multi-layer structure comprising an MDO multi-layer film, a first layer, and a sealant layer is formed into a pouch. The pouches were heat sealed at a cross seal temperature of 110 ℃, a long seal temperature of 120 ℃ and a dwell time of 300 milliseconds (ms). The total thickness of the multilayer film was 50. Mu.m. The pouches were sealed at a rate of 60 pouches per minute ppm and each pouch had a length of 240 millimeters (mm). The pouch showed a hermetic seal and was considered to have a good visual appearance when tested on a Bosch (Bosch) VFF sealing line.

Example 2: thermal bonding

In addition, the multilayer films were tested for hot tack strength. The operating conditions were as follows: sealing pressure of 0.5N/mm ² The sealing time was 0.5 seconds, the cooling time was 0.2 seconds, the peeling speed was 200 mm/sec, and the sample width was 15mm. The results are shown in Table 2. The presence of hot tack at lower temperatures (e.g., 100 ℃) indicates that the heat seal initiation is initiated when the multilayer films of the present invention are at lower temperatures.

TABLE 2

Temperature, [ DEGC]	Thermal adhesion [ N/15mm]
		85	0.31
90	0.47
		95	0.72
100	1.02
		105	1.11
110	1.12
		115	0.99
120	1.03
		130	0.84
140	0.78
		150	0.78
160	0.73

Test method

Unless otherwise specified, the following test methods were used to measure the corresponding properties shown below:

density of

Samples for density measurement should be prepared according to ASTM D4703. The measurement should be made within one hour of pressing the sample according to ASTM D792, method B.

Melting point

Melting point (Tm) should be measured using Differential Scanning Calorimetry (DSC). Differential Scanning Calorimetry (DSC) can be measured on a DSC such as a TA Instruments Q1000 DSC equipped with an RCS cooling accessory and an autosampler. The melting point (Tm) of the sample should be measured according to ASTM D3418.

Heat seal measurement

The films should be heat sealed on a commercial tensile tester according to ASTM F-88 (technique a). The heat seal test is a measure of the seal strength (seal strength) in a flexible barrier material. This is done by measuring the force required to separate the test strip of material containing the seal and identifying Pattern of sample failure. The seal strength is related to the opening force and package integrity. Films were conditioned at 23 ℃ (+2 ℃) and 50% (+5%) r.h. (relative humidity) for a minimum of 40 hours according to ASTM D-618 (procedure a) prior to cutting. Sheets of about 11 inches in length and about 8.5 inches in width were then cut from the three layer coextruded laminate film in the machine direction. The sheet was heat sealed in the machine direction on a Brugger HSG-C sealer at a temperature range: sealing pressure or residence force: 0.138N/mm ² (20 psi) and residence times of 0.3 seconds and 0.5 seconds.

Sealing can be performed in a Brugger HSG-C sealer at a seal bar pressure of 210N with a dwell time of 0.5 seconds. The sealed samples may be tested at 10 inches/minute (4.2 mm/sec or 250 mm/min) in Instron Tensiomer.

Thermal bonding

"Hot tack Strength" and like terms refer to the strength of a heat seal formed between thermoplastic surfaces of a flexible web immediately after the seal is formed and before it cools to ambient temperature. In form-fill operations, the sealed areas of the package are often subjected to damaging forces while still hot. If the heat seal is not sufficiently resistant to these forces, breakage may occur during the packaging process. Hot tack strength, also known as heat seal strength, is a measure of the ability of a material to perform and grade in commercial applications where quality is critical. The hot tack strength may be measured according to ASTM F1921 as follows.

The hot tack initiation temperature refers to a temperature at which the hot tack strength is at least a given threshold strength. For example, the hot tack initiation temperature may be measured at 1.0N/15 mm.

Several aspects are described in this disclosure. The first aspect may be a multilayer structure comprising: (a) A Machine Direction Oriented (MDO) multilayer film comprising (i) a metal layer and (ii) an inner layer in adhering contact with the metal layer, wherein the inner layer comprises: ethylene-vinyl alcohol, polyvinyl alcohol, or both; or a blend of polyethylene with an interpolymer of ethylene and methyl acrylate, ethyl acrylate, or a carboxylic acid; (b) A first layer extruded onto the metal layer of the longitudinally oriented multilayer filmWherein the interpolymer has a melt index (I) of from 5g/10 min to 20g/10 min ₂ ) An acid content of 1 to 10 wt% and a melting temperature of 90 to 100 ℃; and (c) a sealant layer in adhering contact with the first layer, wherein the sealant layer comprises a polyethylene having a melt index (I) of 3g/10 min to 30g/10 min ₂ ) And a heat seal initiation temperature of 95 ℃ or less.

Another aspect may include any other previously disclosed aspect wherein the metal layer is a metallization layer comprising aluminum or an oxide of silicon.

Another aspect may include any other previously disclosed aspect, wherein the interpolymer of the first layer is a terpolymer of: ethylene; acrylic acid or methacrylic acid; and alkyl acrylates.

Another aspect may include any other previously disclosed aspect, wherein the interpolymer of the first layer comprises from 50% to 98% by weight ethylene.

Another aspect may include any other previously disclosed aspect wherein the sealant layer comprises 15 wt% to 40 wt% low density polyethylene based on the total weight of the sealant layer.

Another aspect may include any other previously disclosed aspect wherein the sealant layer further comprises 60 to 85 weight percent of a propylene-based plastomer having a density of 0.890g/cc or less and a melt flow rate of at least 8g/10 minutes (at 230 ℃ and 2.16 kg).

Another aspect may include any other previously disclosed aspect, wherein the sealant layer further comprises 60 to 85 weight percent of at least one polyethylene having a density of 0.870 to 0.911g/cc and a melt index (I2) of at least 3g/10 minutes.

Another aspect may include any other previously disclosed aspect wherein the MDO multilayer film has one or more polyethylene layers.

Another aspect may include an article comprising a multilayer structure according to any of the previously disclosed aspects. In another aspect, the article is a pouch.

It should also be noted that references herein to "at least one" component, element, etc. are not intended to be interpreted as implying that the use of the article "a" or "an" is intended to be limited to a single component, element, etc.

Having described the subject matter of the present disclosure in detail and by reference to specific embodiments thereof, it should be noted that the various details disclosed herein should not be construed as implying that such details relate to elements which are essential elements of the various embodiments described herein, even if the specific elements are shown in each of the accompanying drawings accompanying the present description. Further, it will be apparent that modifications and variations are possible without departing from the scope of the present disclosure, including but not limited to the embodiments defined in the appended claims. More specifically, although some aspects of the present disclosure are identified herein as preferred or particularly advantageous, it is contemplated that the present disclosure is not necessarily limited to these aspects.

It should be noted that one or more of the appended claims utilize the term "wherein" as a transitional expression. For the purposes of defining the present invention, it is noted that this term is introduced in the claims as an open transitional phrase that is used to introduce a recitation of a series of features of the structure and should be interpreted in the same manner as a more commonly used open-ended leading term "comprising".

Claims

1. A multilayer structure, the multilayer structure comprising:

(a) A Machine Direction Oriented (MDO) multilayer film comprising (i) a metal layer and (ii) an inner layer in adhering contact with the metal layer, wherein the inner layer comprises:

ethylene-vinyl alcohol, polyvinyl alcohol, or both; or (b)

Blends of polyethylene with interpolymers of ethylene and:

the composition of the methyl acrylate is prepared from the methyl acrylate,

ethyl acrylate, or

A carboxylic acid;

(b) A first layer extruded onto the metal layer of the machine direction oriented multilayer film,

wherein the first layer comprises an interpolymer of ethylene and acrylic acid or methacrylic acid, wherein the interpolymer has a melt index (I) from 5g/10 min to 20g/10 min ₂ ) An acid content of 1 to 10 wt% and a melting temperature of 90 to 100 ℃; and

(c) A sealant layer in adhering contact with the first layer, wherein the sealant layer comprises a polyethylene having a melt index (I) of 3g/10 min to 30g/10 min ₂ ) And a heat seal initiation temperature of 95 ℃ or less.

2. The multilayer structure of claim 1, wherein the metal layer is a metallization layer comprising aluminum or an oxide of silicon.

3. The multilayer structure of claim 1 or 2, wherein the interpolymer of the first layer is a terpolymer of: ethylene; acrylic acid or methacrylic acid; and alkyl acrylates.

4. The multilayer structure of any preceding claim wherein the interpolymer of the first layer comprises from 50 to 98 weight percent ethylene.

5. The multilayer structure of any preceding claim, wherein the sealant layer comprises 15 to 40 wt% low density polyethylene based on the total weight of the sealant layer.

6. The multilayer structure of any preceding claim, wherein the sealant layer further comprises from 60 wt% to 85 wt% propylene-based plastomer having a density of 0.890g/cc or less and a melt flow rate of at least 8g/10 minutes (at 230 ℃ and 2.16 kg).

7. The multilayer structure of any preceding claim, wherein the sealant layer further comprises from 60 to 85 weight percent of at least one polyethylene having a density of from 0.870g/cc to 0.911g/cc and a melt index (I2) of at least 3g/10 minutes.

8. The multilayer structure of any preceding claim, wherein the MDO multilayer film has one or more polyethylene layers.

9. An article comprising the multilayer structure of any preceding claim.

10. The article of claim 9, wherein the article is a pouch.